If I could go back a second time (and third, and fourth) to undo or alter the changes I made if I didn’t like the results, then I would do it. Otherwise, I wouldn’t. Why not? Because to save 75 million people I would be risking everyone alive on earth today. Seriously - I can easily speculate alternate histories in which everyone dies. That’s too big a risk to take if there are no undo’s.
I agree with begbert. From a risk-reward standpoint it’s not worth it. It’s a horrific gamble.
If I could undo it all without consequence if I didn’t like the results, it’d be worth a try.
I would have to go with no. The Black Death killed 75 million people 700 years ago. The impact on history of that not happening is pretty fricken huge. The world as we know it would not exist. And there is no reason to think the alternative would be better then the world we live in now.
I’m not even going to get into the fact that you may have just violated causality by creating a world in which you were never born(and thus could have never gone back in time to stop the black plague).